Systems and methods for fabrication of orthodontic aligners

ABSTRACT

Orthodontic positioning devices, and related methods and systems, are disclosed for use with one or more orthodontic elastic members. The disclosed methods may comprise determining the geometries for a pair of orthodontic aligners for use as part of an orthodontic treatment plan. The geometries for the pair of orthodontic aligners may include an upper aligner with a first marking and a lower aligner with a second marking. The first marking may correspond to a position of a first hook, and the second marking may correspond to a position of a second hook. The first hook and the second hook may be configured to engage with an orthodontic elastic member so as to react a force to, for example, generate orthodontic forces on the patient’s teeth.

CROSS-REFERENCE

This application is a continuation of U.S. Application No. 17/884,972,filed Aug. 10, 2022, which is a continuation of U.S. Application No.17/227,158, filed Apr. 9, 2021, now U.S. Pat. No. 11,471,250, issuedOct. 18, 2022, which is a continuation application of U.S. ApplicationNo. 17/163,144, filed Jan. 29, 2021, which is a continuation applicationof U.S. Application No. 16/285,004, filed Feb. 25, 2019, now U.S. Pat.No. 10,912,627, issued Feb. 9, 2021, which is a continuation applicationof U.S. Application No. 14/951,245, filed Nov. 24, 2015, now U.S. Pat.No. 10,271,923, issued Apr. 30, 2019, which is a divisional applicationof U.S. Application No. 12/772,130, filed Apr. 30, 2010, now abandoned,each of which are incorporated herein by reference in their entirety andto which applications we claim priority under 35 U.S.C. § 120.

BACKGROUND

The present invention relates generally to the field of orthodontics,and more particularly to dental positioning appliances configured tointerface with an orthodontic elastic member and react a force from theelastic member into the appliance.

An objective of orthodontics is to move a patient’s teeth to positionswhere function and/or aesthetics are optimized. Traditionally,appliances such as braces are applied to a patient’s teeth by a treatingpractitioner and the set of braces exerts continual force on the teethand gradually urges them toward their intended positions. Over time andwith a series of clinical visits and adjustments to the braces, thepractitioner adjusts the appliances to move the teeth toward their finaldestination.

More recently, alternatives to conventional orthodontic treatment withtraditional affixed appliances (e.g., braces) have become available. Forexample, systems including a series of preformed appliances/alignershave become commercially available from Align Technology, Inc., SantaClara, CA, under the tradename Invisalign® System. The Invisalign®System is described in numerous patents and patent applications assignedto Align Technology, Inc. including, for example in U.S. Pat. Nos.6,450,807, and 5,975,893, as well as on the company’s website, which isaccessible on the World Wide Web (see, e.g., the url“www.invisalign.com”). The Invisalign® System includes designing and/orfabricating multiple, and sometimes all, of the aligners to be worn bythe patient before the aligners are administered to the patient and usedto reposition the teeth (e.g., at the outset of treatment). Often,designing and planning a customized treatment for a patient makes use ofcomputer-based 3-dimensional planning/design tools, such as Treat™software from Align Technology, Inc. The design of the aligners can relyon computer modeling of a series of planned successive tootharrangements, and the individual aligners are designed to be worn overthe teeth and elastically reposition the teeth to each of the plannedtooth arrangements.

While recently developed orthodontic treatment technologies, such asthose described above, represent a considerable advancement in the fieldof orthodontics, additional advancements remain of interest. Forexample, in some instances it may be advantageous to use an orthodonticelastic member to generate a tension force between a patient’s upper andlower teeth to bring the teeth into a desired occlusion. In sometraditional approaches, brackets are bonded to the teeth and anorthodontic elastic member is used to couple the brackets to generatethe tension force. Generating such a tension force in conjunction withrecently developed orthodontic approaches can be challenging. Forexample, shell aligners are generally designed to match the geometry ofa patient’s teeth, thereby leaving little room for bonding such bracketsto a patient’s teeth. As such, there is a need for shell aligners thatcan be used in conjunction with an orthodontic elastic member to, forexample, bring a patient’s teeth into a desired occlusion.

BRIEF SUMMARY

The present disclosure provides orthodontic positioning appliances foruse with an orthodontic elastic member, and related systems and methods.The disclosed positioning appliances are configured to couple with anorthodontic elastic member so as to react a force from the elasticmember into the appliance. Such appliances can advantageously employ theforce imparted by the elastic member to apply desired repositioningforces to a patient’s teeth to, for example, generate a desiredocclusion and/or supplement repositioning forces generated by theappliance.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the ensuing detailed descriptionand accompanying drawings. Other aspects, objects and advantages of theinvention will be apparent from the drawings and detailed descriptionthat follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a jaw and an incremental positioning appliance forthe jaw, in accordance to an embodiment.

FIG. 2A illustrates upper and lower teeth received within incrementaltooth positioning appliances having gingivally disposed hooks, inaccordance to an embodiment.

FIG. 2B illustrates upper and lower teeth received within incrementaltooth positioning appliances having gingivally disposed hooks, whereinthe hooks are configured to angle or curve more toward a tooth’ssurface, in accordance with an embodiment.

FIG. 3A illustrates teeth received within teeth receiving cavities of anincremental tooth positioning appliance and an orthodontic elasticmember coupled with the positioning appliance. The appliance includesnotches or hooks cut or formed into a tooth receiving cavity of theappliance.

FIG. 3B is a cross-sectional view of a tooth and the positioningappliance of FIG. 3A illustrating hook displacement induced by theorthodontic elastic member.

FIG. 4A is a cross-sectional view of an incremental tooth positioningappliance having an offset hook, in accordance with an embodiment of thepresent invention.

FIG. 4B illustrates a tooth received within a tooth receiving cavity ofthe incremental tooth positioning appliance of FIG. 4A and anorthodontic elastic member coupled with the offset hook, in accordancewith an embodiment of the present invention.

FIG. 4C illustrates a reinforced version of the offset hook of FIG. 4A,in accordance with an embodiment of the present invention.

FIG. 5 illustrates a tooth received within a tooth receiving cavity ofan incremental tooth positioning appliance having a gingivally disposedoffset hook and an orthodontic elastic member coupled with thegingivally disposed hook, in accordance with an embodiment of thepresent invention.

FIG. 6 illustrates a reinforced version of the gingivally disposed hookof FIG. 5 , in accordance with an embodiment of the present invention.

FIG. 7 illustrates a tooth received within a tooth receiving cavity ofan incremental tooth positioning appliance having a gingivally disposedoffset hook and an orthodontic elastic member coupled with thegingivally disposed hook, in accordance with an embodiment of thepresent invention.

FIG. 8A illustrates teeth received within teeth receiving cavity of anincremental tooth positioning appliance having an exterior hook and anorthodontic elastic member coupled with the exterior hook, in accordancewith an embodiment of the present invention.

FIG. 8B is a cross-sectional view of a tooth and the positioningappliance of FIG. 8A illustrating the orthodontic elastic member coupledwith the exterior hook, in accordance with an embodiment of the presentinvention.

FIG. 9A illustrates teeth received within teeth receiving cavities of anincremental tooth positioning appliance having a gingivally disposedexterior hook and an orthodontic elastic member coupled with thegingivally disposed exterior hook, in accordance with an embodiment ofthe present invention.

FIG. 9B is a cross-sectional view of a tooth and the positioningappliance of FIG. 9A illustrating the orthodontic elastic member coupledwith the gingivally disposed exterior hook, in accordance with anembodiment of the present invention.

FIG. 10 illustrates an incremental tooth positioning appliance having areinforcing corrugation and an exterior hook coupled with an orthodonticelastic member, in accordance with an embodiment of the presentinvention.

FIG. 11 is a simplified block diagram illustrating a method forfabricating an aligner having an exterior hook using a mold, inaccordance with an embodiment of the present invention.

FIGS. 12A and 12B illustrate the addition of a hook edge (12A) and awitness object (12B) to mold geometry used to generate an appliancehaving an offset hook, in accordance with an embodiment of the presentinvention.

FIG. 13 is a simplified block diagram illustrating a method for directfabrication of an aligner having an exterior hook, in accordance with anembodiment of the present invention.

FIG. 14 diagrammatically illustrates a fabrication system in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. However, it will also be apparent toone skilled in the art that the present invention may be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

Orthodontic positioning appliances are provided that can be used inconjunction with one or more orthodontic elastic members, as well asrelated methods and systems. During orthodontic treatment, it may benecessary to apply forces to a tooth to generate movement of the toothto, for example, bring the patient’s teeth into a better occlusion. Thepresently disclosed appliances, methods, and systems provide means bywhich such forces can be applied during orthodontic treatment whereappliances having teeth receiving cavities are used, such as preformedappliances/aligners available from Align Technology, Inc., Santa Clara,CA, under the tradename Invisalign® System.

The disclosed orthodontic positioning appliances for use with anorthodontic elastic member include, for example, a patient removabletooth positioning appliance having teeth receiving cavities shaped toreceive and apply a resilient positioning force to a patient’s teeth.The positioning appliance can include a hook configured to interfacewith an orthodontic elastic member so as to react a force from theelastic member into the patient-worn appliance, thereby applying (e.g.,supplementing) forces other than or in addition to the forces applied tothe patient’s teeth and generated solely by the positioning appliance(s)in the absence of the coupled elastic member. The appliance and/or hookthereof can be configured to more optimally engage an elastic memberwhen the appliance is worn by the patient. In one embodiment, forexample, the hook can be configured to be laterally offset from anotherportion of the appliance, such as a portion of the appliance thatengages the patient’s teeth when worn. For example, a hook can be offset(e.g., laterally offset) from a portion of the appliance that engages abuccal surface of a tooth when the appliance is coupled with thepatient’s teeth. In such an embodiment, the hook will be offset evenwhen no orthodontic elastic member is coupled with the tooth.

In another embodiment, an appliance can be configured such that the hookis gingivally offset from a portion of the appliance. For example,certain shell-type appliances will include a gingival edge or edge ofthe appliance that, when worn by a patient, is disposed substantiallyalong the gingival line or margin where gingival tissue meets the toothcrown at the base of the tooth. In certain embodiments, a hook of anappliance will be gingivally offset or offset in a gingival directionrelative to the gingival edge of the appliance. Such a configurationadvantageously allows incorporation of the hook into the appliancestructure, but without necessarily reducing tooth receiving/engagingsurfaces of an appliance cavity.

An appliance can include a reinforcement structure selected and/ordisposed on the appliance so as to stiffen the appliance against lateraldeflection induced by the force from the elastic member. For example, aportion of the appliance can include a corrugation to stiffen theappliance. In another embodiment, the appliance can include a locallystiffened area (e.g., via an added shape or contour) connected with thehook to stiffen the hook against deflection (e.g., lateral deflection)induced by the force from the elastic member.

Referring now to the drawings, in which like reference numeralsrepresent like parts throughout the several views, FIG. 1 provides anappropriate starting point in a discussion of the present invention withrespect to tooth repositioning appliances designed to applyrepositioning forces to teeth. A tooth repositioning appliance 10 can beworn by a patient in order to achieve an incremental repositioning ofindividual teeth in the jaw 11. The appliance can include a shell (e.g.,polymeric shell) having teeth-receiving cavities that receive andresiliently reposition the teeth. In many embodiments, a polymericappliance can be formed from a thin sheet of suitable elastomericpolymeric material, such as 0.03-inch thermal forming dental material byTru-Tain Plastics, Rochester, Minnesota. An appliance can fit over allteeth present in an upper or lower jaw, or less than all of the teeth.In some cases, only certain teeth received by an appliance will berepositioned by the appliance while other teeth can provide a base oranchor region for holding the appliance in place as it applies forceagainst the tooth or teeth targeted for repositioning. In some cases,many or most, and even all, of the teeth will be repositioned at somepoint during treatment. Teeth that are moved can also serve as a base oranchor for holding the appliance as it is worn by the patient.Typically, no wires or other means will be provided for holding anappliance in place over the teeth. In some cases, however, it may bedesirable or necessary to provide individual anchors on teeth withcorresponding receptacles or apertures in the appliance so that theappliance can apply a selected force on the tooth. Exemplary appliances,including those utilized in the Invisalign® System, are described innumerous patents and patent applications assigned to Align Technology,Inc. including, for example in U.S. Pat. Nos. 6,450,807, and 5,975,893,as well as on the company’s website, which is accessible on the WorldWide Web (see, e.g., the url “www.invisalign.com”).

An appliance can be designed and/or provided as part of a set orplurality of appliances. In such an embodiment, each appliance may beconfigured so a tooth-receiving cavity has a geometry corresponding toan intermediate or final tooth arrangement intended for the appliance.The patient’s teeth can be progressively repositioned from an initialtooth arrangement to a target tooth arrangement by placing a series ofincremental position adjustment appliances over the patient’s teeth. Atarget tooth arrangement can be a planned final tooth arrangementselected for the patient’s teeth at the end of all planned orthodontictreatment. Alternatively, a target arrangement can be one of manyintermediate arrangements for the patient’s teeth during the course oforthodontic treatment, which may include where surgery is recommended,where inter-proximal reduction (IPR) is appropriate, where a progresscheck is scheduled, where anchor placement is best, where palatalexpansion is desirable, etc. As such, it is understood that a targettooth arrangement can be any planned resulting arrangement for thepatient’s teeth that follows one or more incremental repositioningstages. Likewise, an initial tooth arrangement can be any initialarrangement for the patient’s teeth that is followed by one or moreincremental repositioning stages. The adjustment appliances can begenerated all at the same stage or in sets or batches, e.g., at thebeginning of a stage of the treatment, and the patient wears eachappliance until the pressure of each appliance on the teeth can nolonger be felt or has resulted in the maximum amount of expressed toothmovement for that given stage. A plurality of different appliances(e.g., set) can be designed and even fabricated prior to the patientwearing any appliance of the plurality. After wearing an appliance foran appropriate period of time, the patient replaces the currentappliance with the next appliance in the series until no more appliancesremain. The appliances are generally not affixed to the teeth and thepatient may place and replace the appliances at any time during theprocedure (e.g., patient-removable appliances). The final appliance orseveral appliances in the series may have a geometry or geometriesselected to overcorrect the tooth arrangement, i.e., have a geometrywhich would (if fully achieved) move individual teeth beyond the tootharrangement which has been selected as the “final.” Such over-correctionmay be desirable in order to offset potential relapse after therepositioning method has been terminated, i.e., to permit movement ofindividual teeth back toward their pre-corrected positions.Over-correction may also be beneficial to speed the rate of correction,i.e., by having an appliance with a geometry that is positioned beyond adesired intermediate or final position, the individual teeth will beshifted toward the position at a greater rate. In such cases, the use ofan appliance can be terminated before the teeth reach the positionsdefined by the appliance.

During a course of orthodontic treatment, it may be necessary to apply aforce to a patient’s teeth to generate movement of the tooth to bringthe patient’s teeth into a better occlusion. In many instances, it maynot be possible to generate desired levels of such a force solelythrough the use of a tooth positioning appliance such as the toothpositioning appliance 10 described above. The forces generated by such atooth positioning appliance can, however, be supplemented by the use ofan orthodontic elastic member.

In accordance with an embodiment of the present invention, anorthodontic appliance, such as those described above, can bedesigned/configured for use in engagement with one or more elasticmembers. Such appliance can be configured to include one or more hooksfor engagement with one or more elastic members. And a set of appliancescan include one or more appliances with hooks.

FIG. 2A illustrates tooth positioning appliances 20, 22 for receiving,respectively, upper and lower teeth of a patient. Appliances 20, 22include hooks 24, 26, respectively. Appliance 20 includes a gingivaledge 25 of the appliance that substantially follows along a gingivalmargin of the patient’s dentition as the appliance 20 is worn.Similarly, appliance 22 includes a gingival edge 27. The hooks 24, 26extend gingivally or in a gingival direction relative to gingival edge25, 27, respectively, and may be pointed in a mesial, distal, orvertical direction in the illustrated embodiment, hook 24 is pointedmesially and hook 26 is pointed distally. As noted above, such agingivally offset configuration can maximize the surface area of thealigner material engaging the tooth received in an adjacent toothreceiving cavity. Hooks 24, 26 may further be offset laterally, e.g., tobetter accommodate an elastic member engaging the hook, as describedfurther herein. In use, an orthodontic elastic member can be coupledbetween the hooks 24, 26, thereby applying a reciprocal force to each ofthe appliances 20, 22. One or more hooks can be incorporated into eachof the appliances 20, 22 to apply one or more forces into theappliances. Such forces can be used to supplement the teethrepositioning forces generated, e.g., by engagement between thepatient’s teeth/tooth surfaces and surfaces of corresponding receivingcavities of the appliances 20, 22.

FIG. 2B illustrates positioning appliances 20, 22. The appliances 20, 22include hooks 24, 26, respectively, wherein the hooks 24, 26 angle orcurve back more toward tooth’s surfaces compared to the embodimentillustrated in FIG. 2A. Hooks as in FIG. 2B may be selected, forexample, to better avoid unwanted contact or poking of the patient’ssoft tissue.

FIG. 3A illustrates teeth 28 received within teeth receiving cavities ofan incremental tooth positioning appliance 30. An orthodontic elasticmember 32 is coupled with the tooth positioning appliance 30 via a hook34 formed by creating a u-shaped aperture 36 located in the side of theappliance. The aperture 36 can be formed into an existing appliance at alocation selected for the transfer of the force from the elastic memberinto the appliance. The aperture 36 can have a slot width and a shapeselected to accommodate the elastic member. A hook 38 can also bepositioned along a gingival margin of the appliance 30. The hook 38 canbe formed, for example, via adjacent slots 40, 42 formed in the gingivalmargin of the appliance 30. Hooks 34 and 38 may be formed by simplycutting or trimming out material from a shell appliance. However, hooksformed by such an approach reduce appliance material or surfacesengaging a tooth received within an adjacent cavity and requiredeflection of appliance material forming the hook in order toaccommodate a positioned elastic member (see, e.g., FIG. 3B).

FIG. 3B is a cross-sectional view of a tooth 28 and the positioningappliance 30 of FIG. 2A. Because the hook 34 is formed via the u-shapedaperture, when the elastic member 32 is coupled with the hook 34, thehook is forced to deflect away from the adjacent surface of the tooth 28to accommodate the presence of the elastic member 32 between the hook 34and the tooth 28. Additional deflection of the hook 34 may be induced bythe force imparted into the hook by the elastic member 32. Suchadditional deflections can be controlled to some extent by shaping theoverall width of the u-shaped aperture to produce a wider hook.

FIG. 4A illustrates an incremental tooth positioning appliance 40 havingan offset hook 42. FIG. 4B illustrates a tooth 28 received within atooth receiving cavity of the incremental tooth positioning appliance 40and an orthodontic elastic member 32 coupled with the offset hook 42.The offset hook 42 is offset from an adjacent surface of the tooth 28(e.g., buccal surface, lingual surface) when the appliance 40 is coupledwith the patient’s teeth and no orthodontic elastic member is coupledwith the hook. The offset can be configured to accommodate an elasticmember with reduced deflection, in contrast to the hook 34 or 38 ofFIGS. 3A and 3B. The hook 42 can be shaped to retain the elastic memberin the absence of the elastic member being coupled with an opposing archof the patient teeth. For example, the hook 42 can be shaped to trap theelastic member in contact with the surface of the tooth 28 (e.g., via ahook shaped to engage a sufficient portion of the perimeter of theelastic member), while still allowing installation of the elastic memberinto the trapping engagement of the hook 42 via an opening 46. Thelateral offset may be configured such that the opening 46 is closer tothe tooth than the maximum offset distance, in order that the offsetallows the elastic to be engaged against the aligner without touchingthe tooth, but the hook does not protrude towards the soft tissue,thereby making the hook comfortable for the patient.

In one example, the tip of the hook may curve or angle away from softtissue or back toward the tooth surface. The tip of the hook may also becurved, angled, or bent towards the gingival line such that the elasticmay be placed into the aligner first before the aligner is worn, and thehook angle/curvature keeps the elastic from falling off of the aligner.

The appliance 40 can optionally include a reinforcement structure in thevicinity of the hook 42 to reduce deflection induced by the force fromthe elastic member 32. For example, as illustrated in FIG. 4C, theappliance 40 can include a locally strengthened region 48 (e.g., viaincreased thickness in the area of the hook). The appliance 40 can alsobe locally stiffened by embedding a reinforcing structure (e.g., astronger and stiffer material such as stainless steel or plastic resinfiller) into the appliance to reinforce the appliance/hook againstdeflection induced by the force from the elastic member.

As illustrated in FIG. 5 , an offset hook 50 can also be disposedgingivally offset relative to a center of a clinical crown 52 of a tooth28 as received in a cavity proximate to the hook 50, and may begingivally offset relative to a gingival edge of the appliance or agingival margin or line 51 identifying or approximating where gingivaltissue meets the base of the tooth 28 crown. Such a gingival offset canbe used to increase the surface area of the positioning appliance thatengages the tooth 28, as well as to provide space for accommodating anelastic member 32 without necessarily requiring lateral deflection forelastic member engagement. As illustrated in FIG. 6 , an appliancehaving such a gingivally offset hook 50 can include a locally reinforcedarea 54 (e.g., the appliance can be locally thickened in the vicinity ofthe offset hook) to reduce deflection of the hook 50 induced by theforce from the elastic member. The appliance can also be locallystiffened by embedding a reinforcing structure (e.g., a stronger andstiffer material such as stainless steel or plastic resin) into theappliance to reinforce the appliance/hook against deflection induced bythe force from the elastic member.

FIG. 7 illustrates an offset hook 56 that is disposed even moregingivally offset relative to the center of a clinical crown 52 of atooth 28 received in a cavity proximate to the hook 56 than the hook 50shown in FIGS. 5 and 6 . In addition to being more gingivally offset,the hook 56 is also offset further from the adjacent surface of thetooth 28 in order to be disposed at or below a gingival line 58 for thetooth 28. The appliance having such a gingivally offset hook 56 caninclude a locally reinforced area 60 (e.g., the appliance can be locallythickened in the vicinity of the offset hook) to reduce deflection ofthe hook 56 induced by the force from the elastic member 32.

An appliance can be configured with an exterior offset hook that coupleswith an elastic member such that the elastic member does not contact asurface of the tooth. FIGS. 8A and 8B illustrate an exterior offset hook62 positioned similar to the offset hook 42 illustrated in FIGS. 4Athrough 4C. FIGS. 9A and 9B illustrate an exterior offset hook 64 offsetgingivally similar to the offset hook illustrated in FIGS. 5 and 6 . Apositioning appliance can be configured with such an exterior offsethook by incorporating additional material on the exterior of a basicpositioning appliance such as the appliance 10 illustrated in FIG. 1 .Exterior hooks can also be locally reinforced, for example, via locallythickened areas as illustrated in FIGS. 8B and 9B.

A tooth repositioning appliance can also include a reinforcementstructure to stiffen the appliance against deflection induced by theforce from an elastic member. For example, FIG. 10 illustrates arepositioning appliance 70 having a reinforcing corrugation 72 formedalong a gingival edge of the repositioning appliance. The corrugation 72can be formed by adding an elongated protrusion to a male mold prior toforming the appliance over the male mold. A corrugation can be used tostiffen the gingival edge of the repositioning appliance against lateraldeflection induced by the force from the elastic member 32.

The present invention further provides methods for using one or moreorthodontic positioning devices having one or more hooks configured tointerface with an orthodontic elastic member so as to react a force fromthe elastic member into the patient-worn device. The above-describedorthodontic positioning devices can be configured for use in practicingorthodontic treatment or tooth repositioning methods. For example, afirst orthodontic positioning device can be provided, the device havinga hook configured to interface with an orthodontic elastic member isreceived (e.g., by a patient, by a dental professional, etc.), e.g., asdescribed above. The first positioning device is coupled with a firstarch of the patient’s teeth. An orthodontic elastic member is coupledwith the hook of the first positioning device to transfer a force fromthe elastic member into the first positioning device. A secondorthodontic positioning device having a hook configured to interfacewith an orthodontic elastic member is received. The second orthodonticpositioning device is coupled with a second arch of the patient’s teeth,and the orthodontic elastic member that is coupled with the hook of thefirst positioning device is coupled with the hook of the secondpositioning device. Methods can include use of a plurality of different(e.g., successive) positioning devices or appliances.

The present invention further provides systems for repositioning apatient’s teeth. A system can include a plurality of orthodontic toothpositioning appliances. Consistent with discussion provided furtherherein, at least two of the appliances can have different teethreceiving cavities shaped to receive and resiliently reposition thepatient’s teeth in a first arch of the patient’s teeth from a firstarrangement to a successive arrangement. At least one of the appliancesincludes a hook configured to interface with an orthodontic elasticmember so as to react a force from the elastic member into thepatient-worn appliance. The hook can be configured to be offset from asurface of a tooth when the appliance is coupled with the patient’steeth in the first arch and no orthodontic elastic member is coupledwith the hook.

A system can include a plurality of appliances, or sets of appliances,for repositioning a patient’s upper and lower arch teeth. For example,one of a plurality of upper arch appliances and one of a plurality oflower arch appliances can be configured to be worn simultaneously andcoupled with each other via an orthodontic elastic member coupling thehook of the upper arch appliance to the hook of the lower archappliance. The elastic member may also be coupled within the same archin order to connect the elastic to an elastic hook that may be directlybonded to an exposed tooth elsewhere in the arch, whereby the alignerhas been cut around that tooth-affixed elastic hook. The elastic membermay also be coupled from the aligner to an anchorage device attachedsomewhere in the mouth such as a mini-implant or temporary anchoragedevice (TAD) affixed to the patient’s jaw structure.

The present invention further provides methods, such as acomputer-implemented methods, for designing an orthodontic positioningdevice having teeth receiving cavities. Such a method can be used todesign the above-described orthodontic positioning devices. A method caninclude providing and/or receiving a digital representation of thepatient’s teeth in a selected arrangement. The arrangement can beselected to define the shape of teeth receiving cavities shaped toreceive and apply a resilient positioning force to a patient’s teeth. Anappliance can be modeled based on the received representation. Thereceived representation can be used to define the teeth receivingcavities of the appliance. The appliance is modeled to include a hookconfigured to interface with an orthodontic elastic member so as toreact a force from the elastic member into the appliance, including hookdesigns or configurations as indicated further herein. For example, themodeled hook can be configured such that it is offset (e.g., laterally)from a surface of a tooth when the appliance is coupled with thepatient’s teeth and no orthodontic elastic member is coupled with thehook. The hook may alternatively or additionally be gingivally offset,e.g., relative to a gingival edge of the model appliance or a gingivalline of the patient. A reinforcement structure may further be designedor modeled so as to stiffen the appliance against lateral deflectioninduced by the force from the elastic member can optionally be modeledinto the appliance. The reinforcement structure can include, forexample, a corrugation (e.g., positioned along a gingival edge of theappliance to increase the bending stiffness of the gingival edge). Thereinforcement structure can include a locally reinforced area (e.g.,locally thickened) connected with the hook to stiffen the hook againstdeflection induced by the force from the elastic member.

An aligner having an exterior hook can be created using automated steps,manual steps, and/or a combination of automated and manual steps. Suchsteps can include, for example, the removal of material from an alignerassembly (e.g., using a physical cutter such as an end mill, a drill,and a punch; using non-contact removal techniques such as laser cutting,and electrical discharge machining (EDM); using other media such aswater jets, hot water, and hot gases); the addition of material to analigner assembly (e.g., by bonding or attaching a pre-formed featuresuch as a hook); and/or direct fabrication techniques (e.g., stereolithography).

FIG. 11 illustrates a method 100 for indirect fabrication of an alignerhaving a hook by forming a sheet of material over a mold. The geometryof the mold includes representations of a patient’s teeth in anarrangement suitable to generate desired teeth receiving cavities. Awitness object is added to the teeth representations to generate aninner surface of an offset hook portion of the aligner. While some ofthe steps of method 100 are described as being computer-implemented, thealternate use of non-computer implemented approaches may also beapparent to a person of skill in the art. The method 100 can be used togenerate the appliances disclosed above.

In step 102, the position and orientation of an elastic member relativeto the aligner is defined. The defined position and orientation of theelastic member can be generated, for example, using computer-based3-dimensional planning/design tools, such as Treat™ from AlignTechnology, Inc. Computer modeling of one or successive tootharrangements for a patient’s upper and lower teeth can be used toposition/orient an elastic member between an upper jaw appliance hook(or a feature attached to an upper jaw tooth) and a lower jaw appliancehook (or a feature attached to a lower jaw tooth). While the elasticsshown in the figures are oriented generally vertically, otherorientations are possible (e.g., to couple non-occluding pairs ofteeth). An elastic member can be positioned so as to generatesupplemental forces to treat certain types of malocclusions (e.g., classII and III corrections, canine rotation, extrusion, etc.).

In step 104, a hook edge is defined relative to the mold geometry usingthe defined position/orientation of the elastic member. The hook edgedefinition can be a spline on a tooth surface in a 3-dimensional model.The hook edge can be used to position and orient a witness objectcreated in step 106. FIGS. 12A and 12B illustrate a hook edge definitionand a witness object positioned and oriented using the hook edgedefinition and a corresponding tooth surface. The witness object isshaped to generate a suitable offset from the tooth surface to generatea corresponding offset in the inner surface of the aligner. An area ofthe aligner that will interface with the elastic member to hold theelastic member can be determined. Based on the determined area, thewitness object can be created that corresponds to the determined areaand merged into the 3-dimensional representation of the patient’s teeth.The witness object can be merged into a gingival surface included in the3-dimensional representation of the patient’s teeth, and appropriatesmoothing applied. The resulting 3-dimensional representation (moldgeometry) can be used to generate a positive mold over which a sheet ofmaterial is formed to create an aligner.

In step 108, one or more markers can optionally be created/added to themold geometry to generate a reference feature(s) in an aligner that canbe used to guide subsequent removal of material from the aligner (e.g.,see step 118 below) and/or to guide subsequent addition of material tothe aligner (e.g., see step 116 below). Further, a production graphic(s)(e.g., a screenshot on a computer monitor or paper) can optionally begenerated from the mold geometry in step 110 to, for example, guidesubsequent removal of material from the aligner and/or to guidesubsequent addition of material to the aligner.

The mold geometry is then used to create a physical mold, which is usedto form a sheet of elastomeric material to form the aligner. In step112, a mold is created from the 3-dimensional mold geometry. The moldcan be created, for example, directly using automated fabricationtechniques (e.g., stereo lithography). In step 114, the aligner isfabricated by molding a sheet of material over the physical mold.

Once the basic aligner shell is fabricated, material can be optionallyadded and/or removed from the aligner to finalize the geometry of thehook. In step 116, material can be optionally added to the aligner to,for example, form part or all of the hook structure. For example, apreformed feature can be bonded or otherwise attached to the aligner toserve as the hook. In step 118, material can be optionally removed fromthe aligner to complete the formation of the offset hook. For example,localized portions of the aligner can be removed to accommodate theelastic member when installed on the hook.

FIG. 13 illustrates a method 200 for direct fabrication of an alignerhaving a hook, for example, via direct fabrication from a 3-dimensionalrepresentation of the aligner. Suitable direct fabrication techniques(e.g., stereo lithography) can be used. Because some of the steps of themethod 200 are similar to corresponding steps of the method 100 of FIG.11 , detailed description of such steps is not repeated here. While someof the steps of method 200 are described as being computer-implemented,the alternate use of non-computer implemented approaches may also beapparent to a person of skill in the art. The method 200 can be used togenerate the appliances disclosed above.

In step 202, the position and orientation of an elastic member relativeto the aligner is defined. The discussion above regarding step 102 isapplicable to step 202.

In step 204, an aligner shell is defined using a 3-dimensionalrepresentation of a patient’s teeth. A computer program can be used todefine a 3-dimensional representation of the aligner shell usingrepresentations of the patient’s teeth to define the teeth receivingcavities of the aligner shell. The outer surfaces of the aligner shellcan be defined, for example, using suitable offsets from the surfaces ofthe teeth.

In step 206, the definition of the aligner shell is modified toincorporate a hook feature, for example, one of the above disclosed hookfeatures. To provide for efficient incorporation of such a hook feature,pre-defined digital objects can be positioned, oriented, and/or scaledrelative to the aligner shell definition and then merged into thealigner shell definition. Additional material can be added and/orremoved from the resulting aligner definition using known methods.

In step 208, one or more markers can optionally be created/added to thealigner definition as discussed above with respect to step 108 of themethod 100. Likewise, in step 210, production graphics can be createdand used as discussed above with respect to step 110 of the method 100.

In step 212, the resulting 3-dimensional representation of the aligneris used to directly fabricate the aligner. A suitable direct fabricationmethod, such as known rapid prototyping approaches (e.g., stereolithography) can be used.

In step 214, material can be added to the resulting aligner as discussedabove with respect to step 116 of the method 100. Likewise, in step 216,material can be removed from the resulting aligner as discussed abovewith respect to step 118 of the method 100.

An alternative reinforcement technique provides marked regions in therefractory model (the stereolithography model) whereby protrusions orrecessed areas are designed to hold wires and/or plastic resin, whichare inserted into the model, such that when the aligner sheet materialis formed over the model, the reinforcements are “picked up” by theplastic formed over the reinforcements. The aligner is trimmed accordingto specification, leaving the reinforcement embedded into the hookregion of the aligner.

FIG. 14 is a simplified block diagram of a data processing system 300embodying the present invention. Data processing system 300 typicallyincludes at least one processor 302 which communicates with a number ofperipheral devices via bus subsystem 304. These peripheral devicestypically include a storage subsystem 306 (memory subsystem 308 and filestorage subsystem 314), a set of user interface input and output devices318, and an interface to outside networks 316, including the publicswitched telephone network. This interface is shown schematically as“Modems and Network Interface” block 316 and is coupled to correspondinginterface devices in other data processing systems via communicationnetwork interface 324. Data processing system 300 could be a terminal ora low-end personal computer or a high-end personal computer, workstationor mainframe.

The user interface input devices typically include a keyboard and mayfurther include a pointing device and a scanner. The pointing device maybe an indirect pointing device such as a mouse, trackball, touchpad, orgraphics tablet, or a direct pointing device such as a touch screenincorporated into the display. Other types of user interface inputdevices, such as voice recognition systems, are also possible.

User interface output devices typically include a printer and a displaysubsystem, which includes a display controller and a display devicecoupled to the controller. The display device may be a cathode ray tube(CRT), a flat-panel device such as a liquid crystal display (LCD), or aprojection device. The display subsystem may also provide non-visualdisplay such as audio output.

Storage subsystem 306 maintains the basic programming and dataconstructs that provide the functionality of the present invention. Thesoftware modules discussed above are typically stored in storagesubsystem 306. Storage subsystem 306 typically comprises memorysubsystem 308 and file storage subsystem 314.

Memory subsystem 308 typically includes a number of memories, includinga main random access memory (RAM) 310 for storage of instructions anddata during program execution, and a read only memory (ROM) 312 in whichfixed instructions are stored. In the case of Macintosh-compatiblepersonal computers the ROM would include portions of the operatingsystem; in the case of IBM-compatible personal computers, this wouldinclude the BIOS (basic input/output system).

File storage subsystem 314 provides persistent (non-volatile) storagefor program and data files, and typically includes at least one harddisk drive and at least one disk drive (with associated removablemedia). There may also be other devices such as a CD-ROM drive andoptical drives (all with their associated removable media).Additionally, the system may include drives of the type with removablemedia cartridges. The removable media cartridges may, for example behard disk cartridges, such as those marketed by Syquest and others, andflexible disk cartridges, such as those marketed by Iomega. One or moreof the drives may be located at a remote location, such as in a serveron a local area network or at a site on the Internet’s World Wide Web.

In this context, the term “bus subsystem” is used generically so as toinclude any mechanism for letting the various components and subsystemscommunicate with each other as intended. With the exception of the inputdevices and the display, the other components need not be at the samephysical location. Thus, for example, portions of the file storagesystem could be connected via various local-area or wide-area networkmedia, including telephone lines. Similarly, the input devices anddisplay need not be at the same location as the processor, although itis anticipated that the present invention will most often be implementedin the context of PCs and workstations.

Bus subsystem 304 is shown schematically as a single bus, but a typicalsystem has a number of buses such as a local bus and one or moreexpansion buses (e.g., ADB, SCSI, ISA, EISA, MCA, NuBus, or PCI), aswell as serial and parallel ports. Network connections are usuallyestablished through a device such as a network adapter on one of theseexpansion buses or a modem on a serial port. The client computer may bea desktop system or a portable system.

Scanner 320 is responsible for scanning casts of the patient’s teethobtained either from the patient or from an orthodontist and providingthe scanned digital data set information to data processing system 300for further processing. In a distributed environment, scanner 320 may belocated at a remote location and communicate scanned digital data setinformation to data processing system 300 via network interface 324.

Fabrication machine 322 can encompass a range of fabrication machinesand methods used to fabricate positive molds for the above-describedrepositioning appliances or directly fabricate the above-describedrepositioning appliances based on data set information received fromdata processing system 300. In a distributed environment, fabricationmachine 322 may be located at a remote location and receive data setinformation from data processing system 300 via network interface 324.

It is understood that the examples and embodiments described herein arefor illustrative purposes and that various modifications or changes inlight thereof will be suggested to persons skilled in the art and are tobe included within the spirit and purview of this application and thescope of the appended claims. Numerous different combinations or theillustrated or described embodiments are possible, includingcombinations of any aspects of the different described embodiments. Suchcombinations are considered to be part of the present invention.

What is claimed is:
 1. A method of planning an orthodontic treatment,the method comprising: receiving an initial dentition model of apatient’s teeth in an initial arrangement; determining a targetarrangement for the patient’s teeth; generating an orthodontic treatmentplan, wherein the orthodontic treatment plan comprises a plurality ofincremental arrangements to sequentially reposition the patient’s teethfrom the initial arrangement towards the target arrangement;determining, for at least one of the plurality of incrementalarrangements, a geometry corresponding to a pair of orthodonticaligners, wherein the geometries for the pair of orthodontic alignerscomprises: a first plurality of teeth-receiving cavities correspondingto an upper aligner, wherein the first plurality of teeth-receivingcavities are configured to receive at least a portion of the patient’supper dentition; a first marking disposed on the first plurality ofteeth-receiving cavities, wherein the first marking corresponds to aposition of a first hook for receiving a first end of an elastic band; asecond plurality of teeth-receiving cavities corresponding to a loweraligner, wherein the second plurality of teeth-receiving cavities areconfigured to receive at least a portion of the patient’s lowerdentition; a second marking disposed on the second plurality ofteeth-receiving cavities, wherein the second marking corresponds to aposition of a second hook for receiving a second end of the elasticband; and fabricating the pair of orthodontic aligners based on thegeometries determined, wherein fabricating the pair of orthodonticaligners comprises: forming the first plurality of teeth-receivingcavities; forming the first marking on the first plurality ofteeth-receiving cavities; forming the second plurality ofteeth-receiving cavities; and forming the second marking on the secondplurality of teeth-receiving cavities.
 2. The method of planning anorthodontic treatment of claim 1, further comprising forming the firsthook by cutting along the first marking on the first plurality ofteeth-receiving cavities.
 3. The method of planning an orthodontictreatment of claim 1, further comprising forming the first hook bycutting the first plurality of teeth-receiving cavities based on thefirst marking.
 4. The method of planning an orthodontic treatment ofclaim 1, further comprising forming the first hook by manually cuttingthe first plurality of teeth-receiving cavities.
 5. The method ofplanning an orthodontic treatment of claim 1, further comprising formingthe first hook by laser cutting the first plurality of teeth-receivingcavities.
 6. The method of planning an orthodontic treatment of claim 1,wherein the first plurality of teeth-receiving cavities and the firstmarking are formed together in a thermoforming process.
 7. The method ofplanning an orthodontic treatment of claim 1, wherein the first markingcomprises an indentation along the first plurality teeth-receivingcavities.
 8. The method of planning an orthodontic treatment of claim 1,wherein the first marking comprises a protrusion along the firstplurality teeth-receiving cavities.
 9. The method of planning anorthodontic treatment of claim 1, further comprising forming the firsthook by cutting the first plurality of teeth-receiving cavities andforming the second hook by cutting the second plurality ofteeth-receiving cavities; wherein cutting the first plurality ofteeth-receiving cavities comprises removing material along the firstmarking to form a first U-shaped recess as the first hook; and whereincutting the second plurality of teeth-receiving cavities comprisesremoving material along the second marking to form a second U-shapedrecess as the second hook.
 10. The method of providing orthodontictreatment of claim 9, wherein the first U-shaped recess and secondU-shaped recess are oriented in opposing directions.
 11. The method ofproviding orthodontic treatment of claim 1, wherein the first hook ispointed mesially and the second hook is pointed distally.
 12. The methodof providing orthodontic treatment of claim 1, wherein the first hookand the second hook are disposed at positions corresponding to anon-occluding pair of the patient’s teeth.
 13. The method of planning anorthodontic treatment of claim 1, further comprising fabricating a firstpositive mold corresponding to an arrangement of the patient’s upperdentition.
 14. The method of planning an orthodontic treatment of claim1, wherein forming the first plurality of teeth-receiving comprisesthermoforming a sheet of polymeric material over the first positivemold.
 15. A non-transitory computing device readable medium storinginstructions executable by a processor to cause a computing device toperform a method, the method comprising: receiving an initial dentitionmodel of a patient’s teeth in an initial arrangement; determining atarget arrangement for the patient’s teeth; generating an orthodontictreatment plan, wherein the orthodontic treatment plan comprises aplurality of incremental arrangements to sequentially reposition thepatient’s teeth from the initial arrangement towards the targetarrangement; determining, for at least one of the plurality ofincremental arrangements, a geometry corresponding to a pair oforthodontic aligners, wherein the geometries for the pair of orthodonticaligners comprises: a first plurality of teeth-receiving cavitiescorresponding to an upper aligner, wherein the first plurality ofteeth-receiving cavities are configured to receive at least a portion ofthe patient’s upper dentition; a first marking disposed on the firstplurality of teeth-receiving cavities, wherein the first markingcorresponds to a position of a first hook for receiving a first end ofan elastic band; a second plurality of teeth-receiving cavitiescorresponding to a lower aligner, wherein the second plurality ofteeth-receiving cavities are configured to receive at least a portion ofthe patient’s lower dentition; a second marking disposed on the secondplurality of teeth-receiving cavities, wherein the second markingcorresponds to a position of a second hook for receiving a second end ofthe elastic band; and fabricating the pair of orthodontic aligners basedon the geometries determined, wherein fabricating the pair oforthodontic aligners comprises: forming the first plurality ofteeth-receiving cavities; forming the first marking on the firstplurality of teeth-receiving cavities; forming the second plurality ofteeth-receiving cavities; and forming the second marking on the secondplurality of teeth-receiving cavities.
 16. The non-transitory computingdevice readable medium of claim 15, wherein the instructions furthercomprise forming the first hook by cutting along the first marking onthe first plurality of teeth-receiving cavities.
 17. The non-transitorycomputing device readable medium of claim 15, wherein the instructionsfurther comprise forming the first hook by cutting the first pluralityof teeth-receiving cavities based on the first marking.
 18. Thenon-transitory computing device readable medium of claim 15, wherein theinstructions further comprise forming the first hook by laser cuttingthe first plurality of teeth-receiving cavities.
 19. The non-transitorycomputing device readable medium of claim 15, wherein the firstplurality of teeth-receiving cavities and the first marking are formedtogether in a thermoforming process.
 20. The non-transitory computingdevice readable medium of claim 15, wherein the first marking comprisesan indentation along the first plurality teeth-receiving cavities. 21.The non-transitory computing device readable medium of claim 15, whereinthe first marking comprises a protrusion along the first pluralityteeth-receiving cavities.
 22. The non-transitory computing devicereadable medium of claim 15, wherein the instructions further comprise:forming the first hook by cutting the first plurality of teeth-receivingcavities and forming the second hook by cutting the second plurality ofteeth-receiving cavities; wherein cutting the first plurality ofteeth-receiving cavities comprises removing material along the firstmarking to form a first U-shaped recess as the first hook; and whereincutting the second plurality of teeth-receiving cavities comprisesremoving material along the second marking to form a second U-shapedrecess as the second hook.
 23. The non-transitory computing devicereadable medium of claim 22, wherein the first U-shaped recess andsecond U-shaped recess are oriented in opposing directions.
 24. Thenon-transitory computing device readable medium of claim 15, wherein thefirst hook is pointed mesially and the second hook is pointed distally.25. The non-transitory computing device readable medium of claim 15,wherein the first hook and the second hook are positioned on anon-occluding pair of the patient’s teeth.
 26. The non-transitorycomputing device readable medium of claim 15, wherein the geometries aredetermined using a three-dimensional treating planning and design tool.27. A method of planning an orthodontic treatment, the methodcomprising: receiving an initial dentition model of a patient’s teeth inan initial arrangement; determining a target arrangement for thepatient’s teeth; generating an orthodontic treatment plan, wherein theorthodontic treatment plan comprises a plurality of incrementalarrangements to sequentially reposition the patient’s teeth from theinitial arrangement towards the target arrangement; determining, for atleast one of the plurality of incremental arrangements, a geometrycorresponding to an orthodontic aligner, wherein the geometry comprises:a plurality of teeth-receiving cavities configured to receive at least aportion of the patient’s upper or lower dentition; and a markingdisposed on the plurality of teeth-receiving cavities, wherein themarking corresponds to a position of a hook for receiving an end of anelastic band; fabricating the orthodontic aligner based on the geometrydetermined, wherein fabricating the orthodontic aligner comprises:forming the plurality of teeth-receiving cavities; forming the markingon the first plurality of teeth-receiving cavities; and forming the hookby cutting the plurality of teeth-receiving cavities based on themarking; wherein cutting the plurality of teeth -receiving cavitiescomprises manual cutting.
 28. The method of planning an orthodontictreatment of claim 27, further comprising forming the hook by cuttingthe plurality of teeth-receiving cavities based on the marking.
 29. Themethod of planning an orthodontic treatment of claim 27, furthercomprising forming the hook by manually cutting the plurality ofteeth-receiving cavities.
 30. The method of planning an orthodontictreatment of claim 27, wherein the plurality of teeth-receiving cavitiesand the marking are formed together in a thermoforming process.